This invention relates generally to hydraulically operable control valves and in particular it relates to a multi-position flow control valve including a control piston movable in two opposite directions, a spring biasing the piston in one direction into a neutral position and a pressure fluid inlet for hydraulically urging the piston in the opposite direction.
The pressure fluid inlet is controlled via an electrically operable presetting valve that increases or reduces the inlet opening proportionally to an electrical control signal and in this manner it can gradually increase or reduce the inlet flow of the pressure fluid. The quality of the control valve of this type is determined among other factors by the accuracy of reproduction of adjusted values. The recurrent accuracy of the set values depends above all on the precision with which the movable parts subject to frictional losses as well as mutually engageable component parts have been manufactured.
The primary object of this invention is to improve to a substantial degree the accuracy of reproduction of adjusted values in control valves of the above described type.